feat(CF-762): Add Jira integration for session tracking

Sessions now auto-create CF Jira issues on start and post full session
output as comments on end, transitioning the issue to Done.

- Add src/services/jira.ts with createSessionIssue, addComment, transitionToDone
- Update session_start to create CF Jira issue and store key in sessions table
- Update session_end to post session output and close Jira issue
- Add migration 031 to archive local task tables (moved to Jira Cloud)
- Update .env.example with Jira Cloud env vars

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.env.example

@@ -1,4 +1,4 @@
-# Task MCP Environment Variables
+# Session MCP Environment Variables (forked from task-mcp, CF-762)
 
 # PostgreSQL connection via pgbouncer
 POSTGRES_HOST=postgres.agiliton.internal
@@ -7,3 +7,8 @@ POSTGRES_PORT=6432
 # Embedding service configuration
 LLM_API_URL=https://api.agiliton.cloud/llm
 LLM_API_KEY=your_llm_api_key_here
+
+# Jira Cloud (session tracking)
+JIRA_URL=https://agiliton.atlassian.net
+JIRA_USERNAME=your_email@agiliton.eu
+JIRA_API_TOKEN=your_jira_api_token